Double taper tap



Sept. 13, 1938. W. J. HOGG 2,130,182.

DOUBLE TA PER TAP Filed May 22, 1957 6 Sheets-Sheet l W. J, HOGG Sept. 13, 1938.

DOUBLE TAPER TAP Filed May 22, 1957 6 Sheets-Sheet 2 W. J. HOGG Sept. 13, 1938.

DOUBLE TAPER TAP Filed May 22, 1937 6 Sheets-Sheet 5 W. J. HOGG Sept; 13, 1938.

DOUBLE TAPER TAP' Filed May 22, 1937 6 Sheets-Sheet 5 Sept. 13, 1938. w. J. HOGG DOUBLE TAPER TAP Filed May 22, 1957 e shets-sheet 6 l y y G I I o o a H w I c [Ill m. S E). m

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13 tu 'J .L O MSV; i .Q1 -m L Y m m l", ya!! Q. w Gv w @s QF l il l D Patented Sept. 13, 1938 OFFIE DOUBLEA TAPER TAP corporation of Ohio Application May 22, 1937, Serial No. 144,226

20 Claims.

This invention relates to taps particularly adapted to thread pipe couplings, the object of the invention being to provide an improved collapsible or receding tap having automatically shiftable circular cutters or chasers for cutting a double or opposite taper thread in a coupling and which tap is simple in construction and efficient in operation.

A further object of the invention is the provision of a tap in which the same cutters or chasers are used to cut opposite tapers on a coupling or piece of work during a continuous passage through the coupling by rst automatically contracting the chasers and then automatically eX- panding them.

A still further object of the invention`v is the provision of an improved automatically operated tap which is adjustable for diametrical size and length of thread whereby the opposite tapers will correspond at both ends of the coupling in diameter and length and which tap has means for controlling the taper on either end of the work and which will also enable the chasers to cut the correct taper during the finishing of the last few e threads.

A still further object of the invention is the provision of an improved tap in which the cam surfaces controlling the taper of the work are interchangeable to cut tapers beyond the limits of adjustment.

In the drawings accompanying and forming a part of this specication, Fig. 1 is a perspective view of this improved tap.

Fig. 2 is a perspective view of a coupling.

Fig. 3 is a longitudinal view of this improved tap at the beginning of the threading operation.

Fig. 4 is a longitudinal sectional view at right angles to Fig. 3 at the completion of the threading operation and illustrating the chasers in collapsed position.

Fig. 5 is a sectional view similar to that shown in Fig. 4 illustrating the tap at the beginning of the threading operation.

Fig. 6 is a longitudinal sectional view of Fig. 3.

Fig. '7 is a front end View of this improved tap.

Fig. 8 is a section taken on the line 8 8 of Fig. 6 looking in the direction of the arrows.

Fig. 9 is a section taken on the line 9-9 of Fig. 5 looking in the direction of the arrows.

Fig. 10 is a section taken on the line lll-I0 of Fig. 6 looking in the direction of the arrows.

Fig. l1 is a detail of the cam means for controlling the taper.

Fig. 12 is a section taken on line lZ-IZ of Fig. 11 looking in the direction of the arrows.

(Cl. lll- 145) Fig. 13 is a detail of the tripping finger means eifecting the collapse of the tap at the end of the threading operation.

Fig. 14 is a view of the sleeve and core the outer parts removed; and

Fig. 15 is a similar View at right angles to Fig. 14.

Similar characters of reference indicate corresponding parts in the several views.

Before explaining in detail the present improvement and mode of operation thereof, I desire to have it understood that the invention is not limited to details of construction and arrangement of parts illustrated in the accompanying drawings since the invention is capable of other 'v embodiments, and that the phraseology employed is for the purpose of description and not of limitation.

The tap is preferably held against rotation while the work carried in a chuck is rotated by any suitable source of power and the tap is held in a vertical position with the chasers down. The machine is equipped with a lead screw that feeds the carriage down with the tap the correct amount for each revolution of the coupling or work relative tothe pitch of the thread to be cut.

This improved tap, in the preferred form, comprises a housing 2 within which is located a sleeve 3 and within this sleeve is a body l having a head or nose piece 5 which forms a part of the body l and which may be removable if desired.

Within this body 4 is a` core member or piece (i having a hardened tapered front end l provided with lengthwise extending slotted portions 8 of angular formation interlocking' with similarly i formed slotted portions 9 on the inner ends lof the slidingY Chaser blocks i! located circularly around the hardened core 1.

These sliding blocks Il on which the circular chasers or cutters l2 are mounted have their 40 interlocking ends 9 machined to t closely in the slots 8 of the core 5 so that the inward and outward or contractive and expansive movements of the chasers are controlled in a positive manner and accuracy of the cut insured.

This core is preferably made up of two members 6 and 6 adjustably connectedby a threaded stud 6 whereby the position of the member E and also the tension of the spring 38 may be controlled.

The chaser blocks Il are suitably supported in radial recesses oi the body head 5 for radial shiftable or sliding movement by the tapered core l.

The tapered core l may be an integral part of the core member 6 or may be detachable therewith from if desired and be interchangeable to per mit the use of various sizes of cores and the use of any number of circular chasers.

As the body 4 is fed forward or downward in this instance with its chasers I2, the sleeve 3 is carried along and the chasers I2 are fed into the coupling or work to be threaded until an adjustable threaded ring I3 carried by the housing 2 contacts with the'face of the work and stops the forward travel of the housing 2. rIhe adjustment of this ring I3 provides for different lengths of work.

Secured within this housing 2 by a key I1 and screws I8 and I9 is a roller I5, the key projecting through a spiral slot 22' and the roller located in a longitudinally extending groove I6 of the body 4 whereby the housing 2 and body 4 are maintained in line with each other and held against independent rotation when the roller I5 moves in the groove I6 of the body 4.

vAlso located -in the housing 2 is a roller 20 secured Ato--the housing by a pilot screw 2 I. This roller 20 moves in a spiral groove or seat 22 Vof thesleeve 3v and l-whichgroove issimilar in shape to the slot 22 but reverse thereto.

.As fthe tap lbody -4 .moves forward, with the housing 2 held from this forward movement by the Aring.1.3contacting the face of the coupling or work, this roller 20 causes the sleeve 3 to rotate or '.turn yradially reiative to the body 4 and housing .2.

Thesleeve 3.has oppositely located cam grooves 23 forming positive acting cams. As the sleeve 3 isturned-with its cam grooves 23, rollers 24 carriedlonthe ends of a bar 25 projecting through and secured to the-core member 6 and extending through an elongated slot 26 in the body 4, are caused to move forward or backward correspondingitothe `form ofthe-.cam grooves 23,-thereby axially shifting the core and thereby the chaser blocks I.I together with chasers I2 inward and outward causing the chasers to move inward part way and thenroutward part way to cut a double taperin-,the work, so that when the tap gets to the.centerof the coupling, a receding action of the chasers -is Tchanged to an expanding action. These cams 23 are carried by adjustable Yand interchangeablecam plates secured to the sleeve 3 (seeFig. 11).

During the threading operation, a locking spring pressed trigger l21 is held `in a Ygroove 28 of fa-ringl29fcarried in a circular recess 30 in the end of -thelsleeve y3 so that the body 4, sleeve 3 and chasers-12 Iall feed together. This ring 29 is .heldin -the sleeve 3 by means of a ring 3| secured .to theibody bysuitable screws. Suitable anti-friction bearings 32 are located between the parts 3 and 29 so that as the roller 20 moves along 'the-spiral slot .22 of the sleeve 3, excessive pressuremf thetrigger 21 against the side of the groove 28 `of the ring Y29 is eliminated. The trigger 21 bis ,carried by a bracket 21 secured to thebodyby suitable screws.

-Carriedrby the :housing y2 is a tripping finger 33 secured thereto `by-suitable screws and having .fa ,beveled-end l34 in position to engage a roller SSacarriedby-.the-trigger 21 and release the trigger 21 against'the action of its spring 31 (see Fig. f4). This actiontakes place as the cutters finish the threading operation `by reason of the advancing :movement 'of the 'tap carrying the trigger :means Ainto engagement with the finger 33.

When the trigger l21 isreleasedfrom its groove 128 fthesleeve i3 `together with the cams 23, bar

25 and core piece 6 are pulled back by the tension of a spring 38 located in the recess 38 of the body between a collar 39 on the core and a recess wall 4D of the body and this action causes the chaser blocks II together with the chasers I2 t0 recede out of the threads thus collapsing the cutters and permitting the tap to be withdrawn from the coupling or work.

The resetting of the tap is` obtained by suitable means. After the tap is withdrawn from the work, the weight of the housing 2 permits it to V'slide down the sleeve 3 until the roller 2l] contacts the end of the spiral slot 22 in the sleeve 3. As this downward travel takes place, a yoke cooperating with a groove 2 in the housing 2 contacts with a stop on the machine, moving the sleeve 3 downward until the trigger 21 is opposite the slot 28 in the ring 29, when the trigger 21 will be forced into the groove 28 by the action of its spring 31.

The adjustment for size or diameter is obtained as follows:

The trigger 21 is tted within a slot in a wedge shaped block 4U. On each side of this block is positioned a wedge 4I and 42 carried by the bracket .21', each engaged by a screw 43 andi44. Thus, it will be seen that by loosening either screw 43 or 44 and. tightening the other, the block or trigger holder 40 will be moved either forward or backward and with it the ktrigger y21 and sleeve 3, cams 23, bar 25and core piece.6 and owing to the interconnection between the blocks II and tapered core 1, the chasers I2 will be moved either in or out.

When threading a double taper in a piece of work, the control of an equal size at each end is determined by the size at the center of the coupling.

To adjust the point of change of movement from a receding to an expanding action, the ring I3 is threaded in or out of the housing 2.

If it is desired to thread a coupling 91/2," long, it is ynecessary to have the point of change 4%" from the end of the coupling whereas, if a shorter coupling, say 81/2 is to be threaded, the pointof change would have to be 4% from the end of the coupling.

Therefore, in the latter instance, the ring I3 is adjusted out 1/2" beyond the housing so that the housing 2 is moved back 1/2 .before the threading operation commences and then a 41A thread will be cut before the change `to expanding action takes place. Thus, both ends are threaded 4%," from the center of the coupling. A slight variation in size may be made between the two ends by a slight movement of the ring I3. If such'an adjustment of the ring I3 were not made, the receding action of the cutters would result in a taper of 4% and an expanding action of 3% so that the diameter of one end ofthe coupling would be larger than at the other end.

The cams 23 are adjustable for diiferent'tapers and also are interchangeable for tapers beyond their adjustment. For instance, -if a taper per foot .is desired, the spiral camc23 will have centers as illustrated by F, F, F, in Fig. 6 whereas, if-a taperper foot is desired, a new set of cam plates is used having centers :as G, F, G, (see-dotted lines Fig. 6).

`In order to adjust the cams 23 carried by the cam -plates 23 (see Figs. 11 and 12) the angle of the groove may be changed by means of lsuitable adjusting clamps 45 and 46 of wedge Aform (see Fig. 12). These clamps vare in engagement with wedge-shaped portions of 'the cam plates 41 and 48. The clamps 45 and 46 are held in place by a pair of screws 49 and 5U. These clamps and 4B are .located at the end of the cam plates 23 and by loosening one clamp and tightening the other, the angle of the groove can be changed to obtain a faster or slower movement of the core piece 6. rI'he cam can be made in tWo parts so that the taper on one half of the coupling may be changed without changing the taper on the other half.

In practice, to obtain the proper cutting action of the chasers, the chasers are constructed so that the fore part thereof conforms closely to the taper of the threads of the rst half of the coupling while the last few threads conform approximately to the taper of the threads of the last half of the coupling. The taper variesl slightly from the exact taper due to the cutting strains changing the position of the chasers and also due to various materials to be threaded. It has been found that a slightly greater taper on the chaser than the taper required on the work is advantageous in obtaining better formed and smoother threads.

It has also been found in operation that the cutting strain on the chasers is approximately the same all through the threading operation until the last few threads or until the throat of the chasers reaches the end of the coupling. At this time, as the cutting pressure is released, there is an increased taper due to the chasers being allo-wed to expand. To counteract this, the locking trigger 21 is made with a slight bevel o-n its end that ts in the groove 28. This same result could be obtained by beveling the side of the groove 28 or by beveling both as illustrated in Figs. 3, 4, 5 and 6. As the nger 33 moves the trigger 2l out of the groove 28, this bevel permits the sleeve 3 to move rearward, and thus the chasers recede enough to counteract this cutting pressure of the chasers.

The angle 34 on the end of the linger 33 can be made adjustable to suit the length of change in taper and also the bevel on the trigger 2'! can be changed to suit the amount of change in the taper.

It is to be understood that, by describing in detail herein any particular form, structure or arrangement, it is not intended to limit the invention beyond the terms of the several claims of the requirements of the prior art.

Having thus explained the nature of my said invention and described a way of constructing and using the same although without attempting to set forth all of the forms in which it may be made or all of the modes of its use, I claim:

l. A tap comprising a body carrying radially shiftable chasers, a rotatable and axially shiftable sleeve on said body, a housing on the sleeve and having means projecting into the body for preventing independent rotation of the body and housing, means between the housing and sleeve for rotating the sleeve on the relative shiftable movement of said housing and sleeve, a core carried by the body for radially shifting the chasers, and co-operating cam means between the sleeve and core for effecting longitudinal movement of the core in opposite directions thereby rst to recede the chasers and then expand them to cut oppositely tapered threads in the same piece of Work during a single operation.

2. A tap comprising a body carrying radially shiftable chasers, a rotatable and axially shiftable sleeve on said body, a housing on the sleeve and having means projecting into the body for preventing independent rotation of the body and housing, means between the housing and sleeve for rotating the sleeve on the relative shiftable movement of said housing and sleeve, a core carried by the body for radially shifting the chasers, co-operating cam means between the` sleeve and core for effecting longitudinal movement of the core in opposite directions thereby first to recede the chasers and then expand them to cut oppositely tapered threads in the same piece of Work during a single operation, and means co-operating with the sleeve and housing for effecting a collapse of the cutters.

3. A tap comprising a body carrying radially shiftable chasers, a rotatable and axially shiftable sleeve on said body, a housing on the sleeve and having means projecting into the body for preventing independent rotation of the body and housing, means between the housing and sleeve for rotating the sleeve on the relative shiftable movement of said housing and sleeve, a core carried by the body for radially shifting the chasers, co-operating cam means between the sleeve and core for effecting longitudinal movement of the core in opposite directions, thereby first to recede the chasers and then expand them to cut oppositely tapered threads in the same piece of work during a single operation, and adjustable means carried by the housing for effecting a variation in the length of taper to be cut by the cutters,

4. A tap comprising a body carrying radially shiftable chasers, a rotatable and axially shiftable sleeve on said body, a housing on the sleeve and having means projecting into the body for preventing independent rotation of the body and housing, means between the housing and sleeve for rotating the sleeve on the relative shiftable movement of said housing and sleeve, a core carried by the body for radially shifting the chasers, co-operating cam means between the sleeve and core for effecting longitudinal movement of the core in opposite directions thereby rst to recede the chasers and then expand them to cut oppositely tapered threads in the same piece of work during a single operation, and means for adjusting the diameter of the threads tol be cut.

5. A tap comprising a body carrying radially shiftable chasers, a rotatable and axially shiftable sleeve on said body, a housing on the sleeve and having means projecting into the bodyfor preventing independent rotation of the body and housing, means between the housing and sleeve for rotating the sleeve on the relative shiftable movement of said housing and sleeve, a core carried by the body for radially shifting the chasers, co-operating cam means between the sleeve and core for eiTecting longitudinal movement of the core in opposite directions thereby rst to recede the chasers and then expand them to cut oppositely tapered threads in the same piece of work during a single operation, and means for adjusting the diameter of the threads to be cut, said means comprising removable cam means.

6. A tap comprising a body carrying radially shiftable chasers, a rotatable and axially shiftable sleeve on said body, a housing on the sleeve and having means projecting into the body for preventing independent rotation of the body and housing, means between the housing and sleeve for rotating the sleeve on the relative shiftable movement of said housing and sleeve, a core carried by the body for radially shifting the chasers, co-operating cam means between the sleeve and 4core for effecting longitudinal movement ci the core in .opposite directions thereby iirst to recede the chasers and then .expand them to cut oppositely tapered :threads in the same piece of work during a single operation, and means for adjusting `the diameter of the threads to be cut, said means comprising adjustable cam means.

7. `A tap comprising a body carrying radially shiftable chasers, a rotatable and axially shiftable sleeve on said body, a-housing on the sleeve and having means projecting into the body for preventing independent rotation of the body and housing, means between the housing and sleeve for rotating the sleeve on the relative shiftable movement of said housing and sleeve, a core carried by the body for radially shifting the chasers, co-operating cam means between the sleeve and core `for eifecting longitudinal movement of the core in opposite directions thereby first to recede the chasers and then expand them to cut oppositely tapered threads in the same piece of work during a single operation, and means for adjusting the diameter of the threads to be cut, said means comprising adjustable and removable cam means.

8. A tap comprising a body carrying radially shiftable chasers, a sleeve on said body, a housing on the sleeve and having means projecting into the body for preventing independent rotation of the body and housing, said housing and sleeve having relative rotation and axial movement, means between the housing and sleeve for rotating one of said parts on the relative axially shiftable movement of said parts, a core carried by the body for radially shifting the chasers, cooperating cam means between the sleeve and core for effecting longitudinal movement of the core in opposite directions, thereby rst to recede the chasers and then expand them to cut oppositely tapered threads in the same piece oi work during a single operation, means for collapsing the chasers, and means for adjusting said last means thereby to eiTect a change in the diameter of the thread to be cut.

9. A tap comprising a body carrying vradially shiftable chasers, a sleeve on said body, a housing on the sleeve and having means projecting into the body for preventing independent rotation of the body and housing, said housing and sleeve having relative rotation and axial movei ment, means between the housing and sleeve for rotating one of said parts, the housincr or sleeve, cn the relative axially shiftable movement of said parts, a core carried by the body for radially shifting the chasers, and co-operating cam means between the sleeve and core for effecting longitudinal movement of the core in opposite directions, thereby first to recede the chasers and then expandthem to cut oppositely tapered threads in the same piece of work during a single operation.

10. A tap comprising a body carrying radially shiftable chasers, a sleeve on said body, a housing on the sleeve and having means projecting into the body for preventing independent rotation of the body and housing, said housing and sleeve having relative rotation and axial movement, means between the housing and sleeve for rotating one of said parts, the housing or sleeve, on the relative axially shiftable movement of said parts, a core carried by the body for radially shifting the chasers, co-operating cam means between the sleeve and core for effecting longitudinal movement of the core in opposite directions thereby first to recede the chasers and then expand them to cut oppositely tapered threads in the same piece of work during a single operation, and means co-operating with the sleeve and housing for effecting a collapse of the cutters.

ll. A tap comprising a body carrying radially shiftable chasers, a sleeve on said body, a housing on the sleeve and having means projecting into the body for preventing independent rotation of the body and housing, said housing and sleeve having relative rotation and axial movement, means between the housing and sleeve for rotating one of said parts, the housing or sleeve, on the relative axially shiftable movement of said parts, a core carried by the body for radially shifting thechasers, co-operating cam means between the sleeve and core for effecting longitudinal movement of the core in opposite directions, thereby rst to recede the chasers and then expand them to cut oppositely tapered threads in the same piece of work during a single operation, and adjustable means carried by the housing for effecting a variation in the length of taper to be cut by the cutters.

12. A tap comprising a body carrying radially shiftable chasers, a sleeve on said body, a housing on the sleeve and having means projecting .1.

into the body for preventing independent rotation of the body andhousing, said housing and sleeve having relative rotation and axial movement, means between the housing and sleeve for rotating one of said parts, the housing orsleeve, on the relative axially shiftable movement of said parts, a core carried by the body for radially shifting the chasers, co-operating cam means between the sleeve and core for effecting longitudinal movement of the core in opposite directions, thereby iirst to recede the chasers and then expand them to cut oppositely tapered threads in the same piece of work during a single operation, and means for adjusting the diameter of the threads to be cut.

13. A tap comprising a body carrying radially shiftable chasers, a sleeve on said body, a housing on the sleeve and having means projecting into the body for preventing independent rotation of the body and housing, said housing and sleeve having relative rotation and axial movement, means between the housingand sleeve for rotating one of said parts, the housing or sleeve, on the relative axially shiftable movement of said parts. a core carried by the body for radially shifting the chasers, co-operating cam means between the sleeve and core for effecting longitudinal movement of the core in opposite directions thereby first to recede the chasers and then expand them to cut oppositely tapered threads in the same piece of Work during a single operation, and means for adjusting the diameter of the threads to be cut, said means comprising removable cam means.

14. A tap comprising a body carrying radially shiftable chasers, a sleeve on said body, a housing on the sleeve and having means projecting into the body for preventing independent rotation of the body and housing, said housing and sleeve having relative rotation and axial movement, means between the housing and sleeve for rotating one of said parts, the housing or sleeve, on the relative axially shiftable movement of said parts, a core carried by the body for radially shifting the chasers, co-operating cam means bctween the sleeve and core for effecting longitudinal movement of the core in opposite directions, thereby first to recede the chasers and then expand them to cut oppositely tapered threads in the same piece of work during a single operation,

and means for adjusting the diameter of the threads to be cut, said means comprising adjustable cam means.

15. A tap comprising a body carrying radially shiftable chasers, a sleeve on said body, a housing on the sleeve and having means projecting into the body for preventing independent rotation of the body and housing, said housing and sleeve having relative rotation and .axial movement, means between the housing and sleeve for rotating one of said parts, the housing or sleeve, on the relative axially shiftable movement of said parts, a core carried by the body for radially shifting the chasers, co-operating cam means between the sleeve and core for efeoting longitudinal movement of the core in opposite directions, thereby Iirst to recede the chasers and then expand them to cut oppositely tapered threads in the same piece of Work during a single operation, .and means for adjusting the diameter of the threads to be cut, said means comprising adjustable and removable cam means.

16. A tap comprising a body carrying radially shiftable circular chasers, a rotatable and axially shiftable sleeve on said body, a housing on the sleeve and having means projecting into the body for preventing independent rotation of the body and housing, means between the housing and sleeve for rotating the sleeve on the relative shiftable movement of said housing and sleeve, a core carried by the body for radially shifting the chasers, and co-operating cam means between the sleeve and core for effecting longitudinal movement of the core in opposite directions thereby rst to recede the chasers and then expand them to cut oppositely tapered threads in the same piece of work during a single operation.

17. A tap comprising a body carrying radially shiftable circular chasers, a sleeve on said body, a housing on the sleeve and having means projecting into the body for preventing independent rotation of the body and housing, said housing and sleeve having relative rotation and axial movement, means between the housing and sleeve for rotating one of said parts, the housing or sleeve, on the relative axially shiftable movement of said parts, a core carried by the body for radially shifting the chasers, and co-operating cam means between the sleeve and core for eiecting longitudinal movement of the core in opposite directions, thereby rst to recede the chasers and then expand them to cut oppositely tapered threads in the same piece of work during a. single operation.

18. A tap comprising a body having a longitudinally extending slot and carrying radially shiftable chasers, a rotatable and axially shiftable sleeve on said body and having a spirally formed slot and a spirally formed groove, a housing on the sleeve and having means projecting through the spirally formed slot of the sleeve into the slot of the body for preventing independent rotation of the body and housing, means carried by the housing and projecting into the spirally formed groove of the sleeve for rotating the sleeve on the relative axially shiftable movement of said housing and sleeve, a core carried by the body and having a tapered head for radially shifting the chasers, and co-operating cam means between the sleeve and core for effecting longitudinal movement of the core in opposite directions thereby first to recede the chasers and then expand them to cut oppositely tapered threads in the same piece of work during a single operation.

19. A tap comprising a body having'a longitudinally extending slot and carrying radially shiftable chasers, a rotatable and axially shiftable sleeve on said body and having a spirally formed slot and a spirally formed groove, a housing on the sleeve and having means projecting through the spirally formed slots of the sleeve into the slot of the body for preventing independent rotation oi the body and housing, means carried by the housing and projecting into the spirally formed groove of the sleeve for rotating the sleeve on the relative axially shiftable movement of said housing and sleeve, a core carried by the body and having a tapered head for radially shifting the chasers, co-operating cam means between the sleeve and core for effecting longitudinal movement of the corein opposite directions thereby i'lrst to recede the chasers and then expand them to cut oppositely tapered threads in the same piece of work during a single operation, means carried by the body and cooperating with the sleeve and housing for eiecting collapse of the cutters, and means for adjusting said means thereby to eiect a change in the diameter of the thread to be cut.

20. A tap comprising a body carrying radially shiftable chasers, a rotatable and axially shiftable sleeve on said body, a housing on the sleeve and having means projecting into the body for preventing independent rotation of the body and housing, means between the housing and sleeve for rotating the sleeve on the relative shiftable movement of said housing and sleeve, a core carried by the body for radially shifting the chasers, co-operating cam means between the sleeve and core for effecting longitudinal movement of the core in opposite directions thereby rst to recede the chasers and then expand them to cut oppositely tapered threads in the same piece of work during a single operation, means co-operating with the sleeve and housing for electing collapse of the cutters, and means for adjusting said last means thereby to effect a change in the diameter of the thread to be out.

WILLIAM J. I-IOGG. 

